Apparatus for rapid curing of resinous materials

ABSTRACT

Apparatus providing in sequence a heat source for directing a flow of air under pressure at a temperature in the range of 250* to 800*C, a blower to direct a flow of cool air and a drive mechanism to produce motion between the heat source and blower relative to a resinous material to be cured at a speed whereby the material reaches a temperature of at least 170*C within a time interval of less than one minute and is then cooled.

Jan. 1, 1974 United States Patent [191 Panico APPARATUS FOR RAPID CURINGOF F REI N P E Y RESINOUS MATERIALS 0 G AT NTS OR APPLICATIOl\Sl,082,452 9/1967 Great Britain...,.....,......,......... 263/3 [75]Inventor: C. Richard Panico, Medford, Mass.

Assignee: Xenon Corporation, Medford, Mass. Primary E-mmi'fer john CambyAtt0rneyThomas N. Tarrant Filed: Sept. 9, 1971 Appl. No.: 178,936

[57] ABSTRACT Apparatus providing in sequence a heat source for di- [52]U s C] 432/59 recting a flow of air under pressure at a temperature {51Im. c1........ F27b 9/28 in the range of to 800C, a blower to irect a 58Field ofSearch...................... 263/3; 34/23, 24; flow of Cool airand a drive mechanism to produce 432 59 motion between the heat sourceand blower relative to a resinous material to be cured at a speedwhereby the S Ti. 0d 7n 1a mm au .m m m do n ma u. t ms 66 mm 0 t] m r 6SI en mi 6 a emd r k l o a o mm hn mane mw. S T N m A t in. g e CT A rTRS nu RE H N U l 6 5 3 635 454 1/1972 Angelo.............,..... 263/32,236,397 3 1941 Drummond.....,......................... 34/4 9 Claims,1 Drawing gur POWER SUPPLY APPARATUS FOR RAPID CURING OF RESINOUSMATERIALS BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention relates to rapid curing of resin-, ous materials byapplication of heat.

2. Description of the Prior Art The apparatus, according to the presentinvention, has the purpose of curing plastic or resinous materials.Curing, as used herein, is the processing of a plastic or resinousmaterial from a fluid or soft and compliant state to a permanent hard,solid and durable state. Conventionally this is accomplished both by theelimination of solvents and by chemical changes involving interlinkingof molecules commonly known as polymerization. Polymerization is themore advantageous since it does not commonly involve dimensional changesand usually produces a substantial increase in the strength of thematerial. Polymerization is usually caused by the addition of activatingchemicals, by irradiation with some form of wave energy either electricor electromagnetic in nature and/or by heat. One of the greater problemsin polymerization is the time involved. For example, in polymerizing bythe use of heat, the speed is determined largely by the intensity of theheat applied. However, it has been found that the application of highheat usually results either in the formation of inferior polymers havingless complex molecules, lower density and being weak and relativelyfragile, or in the complete destruction of the material. The applicationof low heat and different forms of wave energy results in a delayedcuring process. The use of chemical activators can increase speed but isextremely inconvenient under some conditions.

A large number of plastic materials today are made up of glass fibers orsimilar high durable material which is impregnated with a liquid resinfollowed by curing of the resin. The fibrous material and the resin areusually applied to a form before curing to obtain a desired shape.Recently, preimpregnated materials have become popular consisting of aweb, usually of'fiberglass, in which an uncured resinous material hasbeen impregnated. The preimpregnated material is placed or wrapped uponor about a form or die and then cured to a hard and durable state. Oneapplication for such material that has excited some interest is in theforming and laying of pipe lines. A truck for laying the pipe lineswould not have to carry lengths of pipe but merely rolls of thepreimpregnated material which would be wrapped in a continuous processabout a mandrel, cured and moved along and off the mandrel and into atrench or other location where the pipe line is desired. Any applicationof this sort necessarily requires high curing speeds. p In Van NostrandsScientific Encyclopedia, fourth edition at pages 130 and 131 thedifficulties of rapid polymerization by heat are discussed. Thecross-linking process in polymerization tends to terminate in a rela--tively simple, low weight molecule giving a weak and fragile quality tothe polymer when high heat is used. Thus a maximum temperature of 150Cis recommended. In experimentation, the application of highertemperature causes a visible emission suggesting destruction ordisassociation in the forming polymer. This emission had discouragedfurther testing in this direction.

SUMMARY OF THE INVENTION In accordance with the present invention, ithas been found that apparatus comprising means for delivering a rapidflow of highly heated air to a web of material preimpregnated with apolymerizeable resin so as to raise the temperature of the resin to atleast 170C in a time interval of less than one minute and furthercomprises means to produce relative motion between said preimpregnatedmaterial and said means for delivering a flow of highly heated airwhereby said preimpregnated material will be removed from contact withsaid highly heated air within said time interval of less than oneminute.

Thus it is an object of the invention to provide apparatus for highspeed curing of polymerizable resins impregnated in a fibrous web.

It is a further object of the invention to provide apparatus forcontinuously forming a shaped product from fibrous materialpreimpregnated with polymerizeable resins and curing said resinssimultaneously with said forming.

It is still a further object of the invention to provide apparatus forcontinuous curing of polymerizeable materials in which said materialsmove through the curing stages through a time interval of less than twominutes. Still a further object of the invention is to provide apparatusfor combined heat and electromagnetic radiation for curingpolymerizeable materials at a high rate of speed.

Further objects and features of the invention will become apparent uponreading the following description together with the drawing.

BRIEF DESCRIPTION OF THE DRAWING A diagramatic illustration of apparatusfor manufacturing pipe out of a web of fibrous material preimpregnatedwith polymerizeable resins in accordance with the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT In accordance with one aspect ofthe invention, a continuously cured and rigid pipe can be made in apractical manner at. speeds up to at least 20 feet per minute. Since thespeed in feet per minute is determined largely by the length ofapparatus (the process ing path) the limitation on speed is thepractical length l of processing apparatus. 7

The apparatus as depicted comprises: mandrel 10 extending from supportsleeve 11. Shaft 12 driven by motor 14 extends through support sleeve 11to rotate mandrel 10. Support sleeve 11 is mounted in a further sleeve13. Support sleeve 11 further carries a toothed rack 15 activated byspur gear I6 driven by second motor 17. Spur gear 16 and motor 17 areoperative to drive mandrel 10 in a reciprocating back and forth motion.Motors 14 and 17 are controlled by synchronizer control 18 to correlatethe reciprocation of mandrel 10 with its rotation as required.

Heating element 20,depicted as an electrical resistive heating element,is positioned adjacent to mandrel 10 and a blower 21 is positioned onthe opposite side of heating element 20 from mandrel 10 so as to driveair past heating element 20 and against mandrel 10.

Similarly positioned adjacent to mandrel I0 is a high intensityultraviolet lamp 22 having a reflector 23 to direct the ultravioletradiation from the lamp in the direction of mandrel 10. Ultraviolet lamp22 is suitably of the intermittent arc (flash) type driven by a powersupply 25. Cooling unit 26 is positioned adjacent to mandrel followingheating element 20 to provide a flow of cooling air. Cooling unit 26 asused, provided a flow of ambient air for cooling. However, the purposeis to bring a sharp halt to the temperature rise of the polymerizeableresin and refrigeration should be used when necessary for this purpose.

Housing 35 encloses heating element 20, blower 21 and cooling unit 26 inorder to improve the efficiency of operation. Insulating partition 24separates cooling unit 26 from heating element 20 to reduce overlap.Window 36 in housing 35 facing lamp 22 admits the ultraviolet light.Window 36 is desirably of quartz or other transparent material highlytransparent to UV and resistant to heat.

A plurality of reels depicted by reel 27 and reel 28 are supportedadjacent to mandrel 10 for feeding webs of fiberglass or similar fibrousmaterial preimpregnated with polymerizeable resins to mandrel 10. Thus,as depicted, webs 30 and 31 are fed from reels 27 and 28 respectivelyfor wrapping around mandrel 10.

In operation mandrel 10 is retracted by operation of motor 17 and gear16 until gear 16 arrives at the end of rack adjacent to mandrel 10. Webs30 and 31 are attached to mandrel 10, for example, by masking tape.Heating element 20, blower 21 and cooling unit 26 and ultraviolet lamp22 are all activated as is drive motor 14. Rotation of drive motor 14rotates shaft 12 which in the first part of its rotation expands mandrel10 and then in continuing rotates mandrel 10 so that webs 30 and 31commence winding onto mandrel 10. At the commencement of rotation ofmandrel 10, motor 17 under control of synchronizer control 18 begins aslow advancement of sleeve 11 carrying with it mandrel 10 and the webs30 and 31 wound on mandrel 10. As the mandrel advances, webs 30 and 31are transported past heating element 20 and ultraviolet light 22 whichinitiate rapid polymerization of the polymerizeable resins impregnatingthe webs.

Heating element 20, coacting with blower 21, is of a temperature rangeand size such as to raise the temperature of webs 30 and 31 throughtheir entire thickness to a temperature of at least 170 C. Blower 26following heating element 20 has a shock cooling effect hardening thepipe at a faster rate to prevent deformation as it leaves mandrel 10.When Mandrel 10 is fully extended to the position depicted, motor 14reverses direction and reverse rotation of shaft 12 by internalmechanism (not shown) causes mandrel 10 to collapse to a smallerdiameter thus releasing it from webs 30 and 31. Again under control ofsynchronizer control 18, motor 17 reverses at high speed returningmandrel 10 to the start position from which the process is continued.

Pipe made as depicted may be formed in any number of layers asdetermined by the number of reels 27 and 28 and with some effect onspeed for a given apparatus since the full thickness of the layers mustbe heated to the required temperature.

The exact mechanism of mandrel 10 is not critical to the invention andhas not been illustrated. However, one contemplated form operative inthe apparatus as depicted comprises a mandrel 10 made of expandablesegments internally engaging camming surfaces on a portion of shaft 12within mandrel 10 whereby when shaft rotates in a first direction thecamming surfaces force the segments outwardly until reaching a lockingposition at which point the mandrel must turn with shaft 12. When shaft12 is rotated in the reverse direction, the camming surfaces forceablyretract the expandable segments until a second position is reached asdetected by synchronizing control 18. Motor 14 may be mounted fromsupport sleeve 11 or shaft 12 may be telescopic to allow for thereciprocating motion.

It has been found preferable to have mandrel 10 both highly reflectiveand resistant to adhesion. Thus the surface of mandrel 10 may be metalpolished to a high finish or metal polished to a high finish and thencoated with transparent polytetrafluoroethylene or similar arrangementdesigned to produce high reflectivity and low adherence. The highlyreflective surface has been found particularly desirable with a largenumber of layers forming the product since it increases the heat at theinner layer and also provides a flow surface giving a finished innerproduct surface of glass-like characteristics best suited for flow ofliquid materials as in a pipe.

Original and successful experiments in accordance with the presentinvention were made using prepreg material consisting of a wovenfiberglass web impregnated with an unsaturated polyester mixtureincluding phthalic anhydrides, fumaric and succinic acids, propyleneglycol, cross linking agent and catalyst. Trialalyl cyanurate was usedas a cross linking agent and azo-bisisobutyronitrile was the catalyst.The catalyst was selected for sensitivity to UV radiation. Blowershaving electrical heating elements with nozzle temperatures of 538C madeby Master Appliance Corporation of Racine, Wis. were utilized. Inattempts to raise the temperature of the material quickly without a flowof air under pressure, spot temperatures reached destructive levels andbarrier layers formed preventing the desired rapid temperature rise inthe material as a whole. Strong dense polymers were achieved.

While the invention has been described with relation to a specificembodiment, it is useful in curing similar resinous materials duringshort intervals of time in other arrangements and applications.

Thus it is contemplated that the invention can be used for curingpolymerizeable resins whether or not they are preimpregnated in afibrous web. It is also contemplated that the polymerizeable resin maybe raised rapidly to the temperatures in accordance with the inventionby infrared, rf, microwave and inductive heating. Radiation absorbentparticles may be suspended in the polymerizeable resins for efficientheating by these methods.

Accordingly, it is intended to claim the invention broadly within thespirit and scope of the appended claims.

I claim:

1. Apparatus for curing polymerizeable resins impregnating a fibrous webcomprising:

a. Means to heat gas to a temperature in excess of b. means to drivesaid gas while so heated in a directional manner;

c. means to provide relative motion between said web and said means todrive said gas whereby said gas is directed against said web heatingsaid web and said polymerizeable resins to a temperature of at least C.over a time interval of less than one minute; and,

d. means to reduce said temperature before deterioration of said web andsaid resins.

2. Apparatus for curing polymerizeable resins according to claim 1further comprising means to irradiate said web with high intensity waveenergy.

3. Apparatus for curing polymerizeable resins according to claim 2 inwhich said wave energy is electromagnetic wave energy including at leastpart of the ultraviolet spectrum.

4. Apparatus for curing polymerizeable resins according to claim 1 inwhich said means to provide relative motion is a mandrel for formingsaid web into the shape of an end product.

5. Apparatus for curing polymerizeable resins according to claim 4 inwhich said means to provide relative motion comprises means to rotatesaid mandrel and means to reciprocate said mandrel so as to form acontinuous product.

6. Apparatus for curing polymerizeable resins ac cording to claim 1further comprising additional means to drive cooling gas against saidweb after said heating so as to rapidly cool said web.

7. Apparatus for curing polymerizeable resins according to claim 1wherein said means to provide relative motion comprises means totransport said web past said means to drive said gas within a timeinterval less than one minute.

8. Apparatus for curing polymerizeable resins according to claim 7wherein said means to transport imparts a motion to said web relative tosaid means to drive said gas of at least twenty feet per minute.

9. Apparatus for curing polymerizeable resins ac cording to claim 4further comprising an infrared re flective surface on said mandrel.

1. Apparatus for curing polymerizeable resins impregnating a fibrous webcomprising: a. Means to heat gas to a temperature in excess of 500*C; b.means to drive said gas while so heated in a directional manner; c.means to provide relative motion between said web and said means todrive said gas whereby said gas is directed against said web heatingsaid web and said polymerizeable resins to a temperature of at least170*C. over a time interval of less than one minute; and, d. means toreduce said temperature before deterioration of said web and saidresins.
 2. Apparatus for curing polymerizeable resins according to claim1 further comprising means to irradiate said web with high intensitywave energy.
 3. Apparatus for curing polymerizeable resins according toclaim 2 in which said wave energy is electromagnetic wave energyincluding at least part of the ultraviolet spectrum.
 4. Apparatus forcuring polymerizeable resins according to claim 1 in which said means toprovide relative motion is a mandrel for forming said web into the shapeof an end product.
 5. Apparatus for curing polymerizeable resinsaccording to claim 4 in which said means to provide relative motioncomprises means to rotate said mandrel and means to reciprocate saidmandrel so as to form a continuous product.
 6. Apparatus for curingpolymerizeable resins according to claim 1 further comprising additionalmeans to drive cooling gas against said web after said heating so as torapidly cool said web.
 7. Apparatus for curing polymerizeable resinsaccording to claim 1 wherein said means to provide relative motioncomprises means to transport said web past said means to drive said gaswithin a time interval less than one minute.
 8. Apparatus for curingpolymerizeable resins according to claim 7 wherein said means totransport imparts a motion to said web relative to said means to drivesaid gas of at least twenty feet per minute.
 9. Apparatus for curingpolymerizeable resins according to claim 4 further comprising aninfrared reflective surface on said mandrel.